There is a very good chance that the father is eating them. In new pairs of convicts like mine, they need a lot of practice to be good parents, like any other parents. I've had mine for about 3 months and they lay around every 2 weeks. Their last lay, they finally raised the fry to free-swimming stage, then they got eaten though, or just all died somehow. They laid a few days ago so hopefully they should let them get farther this time.
Just give them sometime and eventually they should beable to raise their young.